MythBusters: Cleanroom Edition

Separating fact from fiction in the world of controlled environment testing

Cleanrooms can feel mysterious, even to the people who work inside them every day. Between the air showers, gowning procedures, and all that talk about ISO classifications, it’s no wonder that myths and half-truths circulate like stray particles in a poorly sealed airlock.

So let’s put on our lab coats (and bunny suits) and bust some of the biggest myths we’ve heard in the field.

Myth #1: “If the particle counter says pass, the cleanroom must be sterile.”

Busted! - Sterility and cleanliness are not the same thing. Particle counters measure non-viable particles — dust, skin flakes, lint, etc. But microbes are viable particles, and they don’t always travel in high enough numbers to affect non-viable counts. A room can “pass” particle counts and still have microbial risks if viable testing isn’t performed.

The truth: Both viable and non-viable testing are needed for a complete picture. One without the other is like checking the scoreboard without watching the game.

Myth #2: “More HEPA filters always means a cleaner room.”

Busted! - HEPA filters are amazing, but simply adding more doesn’t guarantee a higher ISO classification. In fact, overcrowding with too many filters or poorly balanced airflow can create turbulence and dead zones where particles accumulate.

The truth: It’s not about how many HEPA filters you have, but how effectively they’re positioned, sealed, and balanced within the system.

Myth #3: “If the room passed last year, it should pass this year.”

Busted! - Cleanrooms are living, breathing systems — constantly changing with usage, renovations, equipment upgrades, and even subtle shifts in airflow. What was compliant last year may not meet standards this year. That’s why routine re-certification is mandatory, not optional.

The truth: Passing once doesn’t give a permanent hall pass. Controlled environments demand continuous verification.

Myth #4: “Airflow direction tests are just smoke and mirrors.”

Busted! - While it might look like a dramatic smoke show for auditors, airflow visualization is one of the most important tools for identifying turbulence, backflow, or poor placement of equipment. That wisp of smoke can reveal whether product protection is solid — or if contamination risks are sneaking in.

The truth: Smoke pattern testing isn’t a gimmick; it’s a powerful diagnostic tool.

Myth #5: “Cleanrooms are clean no matter what’s happening inside them.”

Busted! - A room can meet ISO 5 standards in a static state (empty, no operators), but look very different in a dynamic state (fully operational, with staff and processes running). Human operators are the single biggest source of contamination in controlled spaces.

The truth: Dynamic testing matters. A cleanroom is only as clean as the people and processes inside it.

Myth #6: “Testing is about getting a pass or fail result.”

Busted! - This one hits close to home. Many clients think testers exist just to stamp a pass/fail grade on their facility. In reality, our role is diagnostic and advisory. We identify risks, provide insights, and help operators maintain environments that protect products and patients.

The truth: Testing isn’t about passing or failing — it’s about protecting lives, science, and integrity.

The Big Takeaway

Controlled environment testing isn’t magic, and it isn’t just about passing a checklist. It’s a science and a practice — built on data, observation, and collaboration between testers, operators, and engineers.

The more we challenge myths, the better the industry gets. And who knows? Maybe the next time you see a puff of smoke in a cleanroom, you’ll think less about “smoke and mirrors” and more about the real magic: science keeping people safe.

Now it’s your turn: What’s the wildest myth you’ve heard about cleanrooms or testing? (Drop it in the comments — let’s bust it together!)